//给你单链表的头指针 head 和两个整数 left 和 right ，其中 left <= right 。请你反转从位置 left 到位置 right 的链
//表节点，返回 反转后的链表 。
//
// 
//
// 示例 1： 
// 
// 
//输入：head = [1,2,3,4,5], left = 2, right = 4
//输出：[1,4,3,2,5]
// 
//
// 示例 2： 
//
// 
//输入：head = [5], left = 1, right = 1
//输出：[5]
// 
//
// 
//
// 提示： 
//
// 
// 链表中节点数目为 n 
// 1 <= n <= 500 
// -500 <= Node.val <= 500 
// 1 <= left <= right <= n 
// 
//
// 
//
// 进阶： 你可以使用一趟扫描完成反转吗？ 
//
// Related Topics 链表 👍 1561 👎 0


package com.leetcode.editor.cn;

import com.leetcode.editor.cn.common.ListNode;

public class P92ReverseLinkedListIi {
    public static void main(String[] args) {
        Solution solution = new P92ReverseLinkedListIi().new Solution();
        ListNode head = new ListNode(1);
        ListNode n2 = new ListNode(2);
        ListNode n3 = new ListNode(3);
        ListNode n4 = new ListNode(4);
        ListNode n5 = new ListNode(5);
        head.next = n2;
        n2.next = n3;
        n3.next = n4;
        n4.next = n5;
        solution.reverseBetween(head, 2, 4);
    }
    //leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     * int val;
     * ListNode next;
     * ListNode() {}
     * ListNode(int val) { this.val = val; }
     * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
     * }
     */
    class Solution {
        public ListNode reverseBetween(ListNode head, int left, int right) {
            if (head == null) return null;
            ListNode emptyNode = new ListNode(-1);
            emptyNode.next = head;
            ListNode start = emptyNode;
            for (int i = 0; i < left - 1; i++) {
                start = start.next;
            }

            ListNode curr = start.next;

            ListNode subHead = curr;

            ListNode end = curr;
            for (int i = 0; i < right - left; i++) {
                end = end.next;
            }
            ListNode tail = end.next;
            end.next = null;

            ListNode pre = null;

            while (curr != null) {
                ListNode temp = curr.next;
                curr.next = pre;
                pre = curr;
                curr = temp;
            }
            start.next = pre;
            subHead.next = tail;
            return emptyNode.next;
        }
    }
//leetcode submit region end(Prohibit modification and deletion)

}